Model Binding With Entity Framework (ASP.NET MVC)

If an EF object has been created outside a context, you need to Attach the object to the context.

See: http://msdn.microsoft.com/en-us/library/bb896271.aspx

I know this is an old thread but in the interest of new readers:

Based on my observations using VS 2012, MVC 4 and EF 4.0 with a view that has an EF object for a model that submits a form back to the controller.

On the controller:

public ActionResult SubmitEFObject(tblData data, FormCollection col)

"data" will only have the properties used in the view (@Html.xxxFor) filled.

It appears that when "data" is created, the posted FormCollection is used to set data's properties. If you had a property that wasn't used, DataID for example, then data.DataID will have a null/default value. Add a "@Html.Hidden(m => m.DataID)" to your view and THEN DataID will be filled.

As a 'quick n dirty' way to work with this, I created a method that would merge the incoming 'data' with the 'data' in the database and return the merged object:

// Note: error handling removed
public tblData MergeWithDB(DBContext db, tblData data, params string[] fields)
{
  tblData d = db.tblData.Where(aa => aa.DataID == data.DataID).Single();
  if (fields.Contains("Field1")) d.Field1 = data.Field1;
  if (fields.Contains("Field2")) d.Field2 = data.Field2;
  if (fields.Contains("Field3")) d.Field3 = data.Field3;
  // etc...
  return d;
}

On the controller:

public ActionResult SubmitEFObject(tblData data, FormCollection col)
{
  DataEntities db = new DataEntities();
  tblData d = MergeWithDB(db, data, col.AllKeys);
  db.SaveChanges();
}

You could make this more generic using reflection or maybe more efficient by looping through the string[] fields instead of all the ifs but for my purposes this was 'good enough'.

Database work should be put in the repository call.

Are you directly binding to an entity framework object in your model binding? If not, you should consider do some mapping between your custom object and entity framework object.